Acoustic noise reduction in a computer system having a vented cover

ABSTRACT

A vented cover includes a pair of cross-flow ventilation ducts each including an acoustic noise reduction lining. The ducts are “cross-flow” in that they cross and bypass one another. The cover is affixed to an enclosure containing components of a computer system and abuts against a panel of the enclosure having an airflow aperture. An air moving device (AMD) passes air through the enclosure from the ducts if the cover is an intake cover, and/or into the ducts if the cover is an exhaust cover. The ducts increase the air path length, and the acoustic absorbing surface, thereby increasing acoustic attenuation. Airflow resistance is reduced by reducing surfaces perpendicular and close to the area where air enters and by reducing sharp turns in the ducts. The cover has a relatively thin depth because the ducts cross and bypass each other in a very space efficient manner.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is a divisional application of U.S. patentapplication Ser. No. 11/304,132, filed Dec. 15, 2005, entitled “METHODAND APPARATUS FOR ACOUSTIC NOISE REDUCTION IN A COMPUTER SYSTEM HAVING AVENTED COVER”, which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates in general to housings for enclosingcomputer systems and in particular to vented covers with acousticattenuation for use with such housings. Still more particularly, thepresent invention relates to a computer system which includes a ventedcover having cross-flow ventilation ducts with an acoustic noisereduction lining.

2. Background Art

Computer systems are using larger amounts of energy, and are generatingmore heat. Increased heat generation is driven by factors such asincreases in processor performance and clock speed, and increases in thenumber of devices per integrated circuit. Electronic components, such asmicroprocessors and integrated circuits, must operate within certainspecific temperature ranges to perform efficiently. Excessive heatdegrades electronic component performance, reliability, life expectancy,and can even cause failure. Air moving devices (AMDs), such as fans andblowers, are widely used for controlling excessive heat. AMDs are oftenused in combination with heat sinks thermally connected to electroniccomponents to be cooled. Typically, heat sinks are formed with fins toincrease the surface area of the heat sink and thereby enhance heatdissipation as air moved by an AMD passes over the heat sink.

In many large server applications, the processors of a computer systemalong with their associated electronics (e.g., memory, disk drives,power supplies, etc.) are packaged in removable drawer configurationsstacked within a rack or frame. In other cases, the processors of acomputer system along with their associated electronics may be in fixedlocations within the rack or frame. Typically, the components are cooledby air moving in parallel air flow paths, usually front-to-back,impelled by one or more AMDs.

With the advent of the increased heat generated by computer systems,increased ventilation is required to move cooling air through thecomputer system. A failure to provide adequate ventilation through acomputer system may increase the probability of computer failure due tooverheating and may result in damage to the electronic components. Dueto the great expense of these electronic components and the concomitantloss of processing time associated with such failures, it is desirablethat adequate ventilation be maintained for computer systems. Increasedair flow rates are needed to provide adequate ventilation. However, theacoustic noise associated with the increased air flow rates required toprovide adequate ventilation, as well as acoustic noise generated by thevarious components within the computer system, represents a problem thatmust be overcome. There are limits on the acoustic output of computersystems (e.g., servers and storage products) set by vendors,governments, standards setting bodies, and the like.

In order to reduce acoustic noise, it is known to utilize an acousticnoise reduction lining in vented covers of computer systems. An exampleof such an arrangement is found in U.S. Pat. No. 5,526,228, issued Jun.11, 1996 to Dickson et al., entitled “COMPUTER SYSTEM UNIT WITH ACOUSTICDAMPENING COOLING FAN SHROUD PANEL”, which is assigned to the assigneeof the present application. As shown in FIG. 1, a cooling fan shroudpanel 101 includes an acoustic noise reduction lining comprising a sideacoustic foam panel 102 and a top acoustic foam panel 104. The acousticdampening cooling fan shroud panel 101 is mounted to an intermediaterear panel 106 of a computer system unit 100. Two cooling fans 108 aremounted within fan mounting apertures of the intermediate rear panel106. The cooling fans 108 draw air through computer system unit 100 froman intake ventilation grill (not shown) of a front panel 110 in thedirection indicated by the arrows designated with reference numeral 111.Mounted within computer system unit 100 are a power supply 112 and anelectronic component package 114, which are cooled by the air drawnthrough computer system unit 100. Air is directed out an exitingventilation aperture 116 of cooling fan shroud panel 101 in thedirection indicated by the arrow designated with reference numeral 117.The exiting ventilation aperture 116 is displaced from the mountingposition of the cooling fans 108 such that acoustic noise resultant fromthe cooling fan operation is diminished. Even though acoustic dampeningcooling fan shroud 101 is effective in diminishing acoustic noise, itexhibits a number of disadvantages. First, the relatively substantialdepth of acoustic dampening cooling fan shroud panel 101 significantlyincreases the footprint of computer system unit 100. Second, the smallarea of exiting ventilation aperture 116 relative to intermediate rearpanel 106 reduces the cooling efficiency.

FIGS. 2 and 3 show other examples of the utilization of acoustic noisereduction lining in vented covers found in the IBM eServer zSeries 900server. As shown in FIG. 2 (Top View), an inlet cover 210 includes anacoustic noise reduction lining comprising two outer acoustic foampanels 212 and central acoustic foam block 214. An inlet ventilationaperture 216 is defined between outer acoustic foam panels 212.Similarly, an exhaust cover 220 includes an acoustic noise reductionlining comprising two outer acoustic foam panels 222 and centralacoustic foam block 224. An exhaust ventilation aperture 226 is definedbetween outer acoustic foam panels 222. The inlet cover 210 and theexhaust cover 220 are mounted to a computer system frame or rack 200using hinges (not shown) so that removable drawers (not shown) stackedwithin computer system frame 200 may be accessed when inlet cover 210and/or exhaust cover 220 is/are swung open via the hinges. AMDs (notshown) draw air through computer system frame 200 from inlet ventilationaperture 216 and exhaust the air through exhaust ventilation aperture226. The air moves in the direction indicated by arrows designated byreference numeral 230. The removable drawers, which contain processorsand their associated electronics, are cooled by the air drawn throughcomputer system frame 200, as are electronic components fixed withincomputer system frame 200. Acoustic noise resultant from the AMDoperation is effectively diminished by inlet cover 210 and exhaust cover220 which have three main attributes: a large amount of acousticabsorbing material; an air/noise path that curves or angles to forcesound to impact the acoustic lining; and minimum sharp bends in the airpath to minimize airflow resistance. Even though inlet cover 210 andexhaust cover 220 are effective in diminishing acoustic noise, theyexhibit a number of disadvantages. First, the relatively substantialdepth of inlet cover 210 and exhaust cover 220 significantly increasethe footprint of computer system frame 200. Second, the central acousticfoam block 224 in the exhaust cover 220 reduces cooling efficiencybecause it acts as a roadblock to exiting air. Third, inlet cover 210and exhaust cover 220 cannot be made much more efficient withoutincreasing airflow resistance, or increasing the cover depth (i.e.,there are practical limits on how deep inlet cover 210 and exhaust cover220 can be while still allowing the hinges to open).

FIG. 3 shows a modification of the configuration of inlet and outletcovers shown in FIG. 2 to reduce increase in the footprint of thecomputer system frame. As shown in FIG. 3, an inlet cover 310 includesan acoustic noise reduction lining comprising two angled outer acousticfoam panels 312 and central acoustic foam panel 314. An inletventilation aperture 316 is defined between angled outer acoustic foampanels 312. Similarly, an exhaust cover 320 includes an acoustic noisereduction lining comprising two angled outer acoustic foam panels 322and central acoustic foam panel 324. An exhaust ventilation aperture 326is defined between angled outer acoustic foam panels 322. The inletcover 310 and the exhaust cover 320 are mounted to a computer systemframe or rack 300 using hinges (not shown) so that removable drawers(not shown) stacked within computer system frame 300 may be accessedwhen inlet cover 310 and/or exhaust cover 320 is/are swung open via thehinges. AMDs (not shown) draw air through computer system frame 300 frominlet ventilation aperture 316 and exhaust the air through exhaustventilation aperture 326. The air moves in the direction indicated byarrows designated by reference numeral 330. The removable drawers, whichcontain processors and their associated electronics, are cooled by theair drawn through computer system frame 300, as are electroniccomponents fixed within computer system frame 300. As with theconfiguration shown in FIG. 2, acoustic noise resultant from the AMDoperation is effectively diminished by inlet cover 310 and exhaust cover320, but with a reduced footprint relative to the configuration shown inFIG. 2. Even though inlet cover 310 and exhaust cover 320 are effectivein diminishing acoustic noise with a reduced footprint, these coversexhibit all of the other of disadvantages of the configuration shown inFIG. 2.

It should therefore be apparent that a need exists for a computer systemenclosure which can both adequately ventilate a computer system housedtherein and reduce the amount of acoustic noise, while addressing thedisadvantages of the prior art.

SUMMARY OF THE INVENTION

According to the preferred embodiments of the present invention, avented cover includes a pair of cross-flow ventilation ducts eachincluding an acoustic noise reduction lining. The ventilation ducts are“cross-flow” in that they cross and bypass one another. The vented coveris affixed to an enclosure containing components of a computer systemand abuts against a panel of the enclosure having an airflow aperture.An air moving device (AMD) passes air through the enclosure from thecross-flow ventilation ducts in the case where the vented cover is anintake ventilation cover, and/or into the cross-flow ventilation ductsin the case where the vented cover is an exhaust ventilation cover. Thecross-flow ventilation ducts increase the air path length, along withthe acoustic absorbing surface, thereby increasing acoustic attenuation.Airflow resistance is reduced by reducing surfaces perpendicular andclose to the area where air enters and by reducing sharp turns in theducts. The vented cover has a relatively thin depth because thecross-flow ventilation ducts cross and bypass each other in a very spaceefficient manner.

The foregoing and other features and advantages of the present inventionwill be apparent from the following more particular description of thepreferred embodiments of the present invention, as illustrated in theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The preferred exemplary embodiments of the present invention willhereinafter be described in conjunction with the appended drawings,where like designations denote like elements.

FIG. 1 is a sectional, partly schematic side view of a computer systemincorporating an acoustic dampening cooling fan shroud panel, as knownin the art.

FIG. 2 is a sectional, top view of a computer system enclosureincorporating vented covers each with an acoustic noise reduction liningthat includes two outer acoustic foam panels and a central acoustic foamblock, as known in the art.

FIG. 3 is a sectional, top view of a computer system enclosureincorporating vented covers each with an acoustic noise reduction liningthat includes two angled outer acoustic foam panels and a centralacoustic foam panel, as known in the art.

FIG. 4 is a top view of a computer system incorporating vented covershaving cross-flow ventilation ducts with an acoustic noise reductionlining according to the preferred embodiments of the present invention.

FIG. 5 is a top view of the computer system shown in FIG. 4, with itsvented covers open.

FIG. 6 is a perspective view of the computer system shown in FIG. 4,including a front vented cover (intake cover) having cross-flowventilation ducts with an acoustic noise reduction lining according tothe preferred embodiments of the present invention.

FIGS. 7 a-7 d are respectively a partial front view; a section, topview; a partial rear view; and a partial side view of a rear ventedcover (exhaust cover) having cross-flow ventilation ducts with anacoustic noise reduction lining according to the preferred embodimentsof the present invention.

FIGS. 7 e-7 g are respectively partial sectional views of the rearvented cover (exhaust cover) shown in FIG. 7 c along sections A-A, B-B,and C-C.

FIGS. 8 a-8 b are respectively a rear view and a section, top view of arear vented cover (exhaust cover) of the having cross-flow ventilationducts with an acoustic noise reduction lining according to the preferredembodiments of the present invention.

FIGS. 9 a-9 b are respectively a front view and a top view of the rearvented cover (exhaust cover) shown in FIGS. 8 a-8 b.

FIG. 10 is a partial, front perspective view of the rear vented cover(exhaust cover) shown in FIGS. 8 a-8 b.

FIG. 11 is a partial, rear perspective view of the rear vented cover(exhaust cover) shown in FIGS. 8 a-8 b.

FIG. 12 is an enlarged partial, rear perspective view of one of the pairof cross-flow ventilation ducts of the rear vented cover (exhaust) shownin FIGS. 8 a-8 b.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 1.0 Overview

In accordance with the preferred embodiments of the present invention, avented cover can include a pair of cross-flow ventilation ducts or aseries of paired cross-flow ventilation ducts each including an acousticnoise reduction lining. The ventilation ducts are “cross-flow” in thatthey cross and bypass one another. The vented cover is affixed to anenclosure containing components of a computer system and abuts against apanel of the enclosure having an airflow aperture. An air moving device(AMD) passes air through the enclosure from the cross-flow ventilationducts in the case where the vented cover is an intake ventilation cover,and/or into the cross-flow ventilation ducts in the case where thevented cover is an exhaust ventilation cover. The cross-flow ventilationducts increase the air path length, along with the acoustic absorbingsurface, thereby increasing acoustic attenuation. Airflow resistance isreduced by reducing surfaces perpendicular and close to the area whereair enters and by reducing sharp turns in the ducts. The vented coverhas a relatively thin depth because the cross-flow ventilation ductscross and bypass each other in a very space efficient manner.

2.0 Detailed Description

With reference to the figures and in particular FIG. 4, there isdepicted a top view of a computer system 400 having a computer systemenclosure 401 which incorporates two vented covers with acoustic noisereduction according to the preferred embodiments of the presentinvention. Although the preferred embodiments of the present inventionare described herein within the context of an enclosure for containing acomputer system, those skilled in the art will appreciate that thepresent invention may be practiced with an enclosure for containing anytype of system. For example, the present invention may be practiced withan enclosure for an air treatment system, such as an air filter, aircleaner, dehumidifier, air conditioner, heater, or the like. Likewise,the present invention may be practiced with an enclosure for containinga computer system different than that shown in FIG. 4. For example, thepresent invention can be applied to enclosures containing computersystems, including personal computers, servers and data storage systems,of various sizes such as small towers (e.g., desktop computer systems),individual rack units and large rack frames (e.g., receiving multipleserver units).

As illustrated in FIG. 4, computer system enclosure 401 preferablyincludes a front panel 402, a rear panel 404, a top panel 406, a bottompanel (not shown), and two side panels 408, 410. However, those skilledin the art will appreciate that computer system enclosure 401 may haveany number and configuration of panels. One or more vented covers 412,414 are also provided according to the preferred embodiments of thepresent invention. As illustrated, vented covers 412, 414 arerespectively mounted at the front and rear of computer system enclosure401. The vented covers 412, 414 include one or more pair of cross-flowventilation ducts, which are described in detail below. Vented cover 412is affixed to computer system enclosure 401 and abuts against frontpanel 402, which has an airflow aperture 403 therein. Similarly, ventedcover 414 is affixed to computer system enclosure 401 and abuts againstrear panel 404, which has an airflow aperture 405 therein. Theconfiguration of vented covers 412, 414 shown in FIG. 4 is illustrative,and the present invention is not limited thereto. The vented covers 412,414 may abut against any panels of the computer system enclosure 401having airflow apertures therein. For example, vented covers 412, 414may be respectively mounted at the side and top of computer systemenclosure 401. Also, a single vented cover may be used (e.g., an exhaustcover, an intake cover, or a combination exhaust/intake cover), or morethan two vented covers may be used.

The vented covers 412, 414 are preferably affixed to computer systemenclosure 401 in a movable or removable manner to allow access tocomputer system components within computer system enclosure 401.Referring now to FIG. 5, vented covers 412, 414 are preferably hingedlyaffixed to computer system enclosure 401 to permit access to removabledrawers when vented covers 412, 414 are swung open. Alternatively,vented covers 412, 414 may be removably mounted to computer system 401,using fasteners such as bolts, screws, clamps or hangers.

With reference now to both FIGS. 4 and 5, computer system enclosure 401provides mechanical support for one or more electronic componentpackages, such as electronics drawers 420. The electronics drawers 420are used to package processors of computer system 400, along with theirassociated electronics (e.g., memory, disk drives, power supplies,etc.). Alternatively, the processors of computer system 400 and theirassociated electronics may be mounted in computer system enclosure 401without being packaged in electronics drawers. Computer system enclosure401 further includes at least one air moving device, such as device 422.In computer system enclosures having multiple electronics drawers, oneor more moving device 422 may be associated with each electronics drawer420. Each air moving device 422 may be physically attached to theelectronics drawer 420 with which it is associated. Alternatively, airmoving devices may be physically attached to computer system enclosure401. Preferably, electronics drawers 420 are slidably mounted withincomputer system enclosure 401, providing easy access to the contents ofelectronics drawers 420 for repair, maintenance, and upgrades.Alternatively, electronics drawers 420 may be permanently mounted withincomputer system enclosure 401, using fasteners such as bolts, screws orclamps.

Referring to FIG. 4, air moving devices 422 cause ambient air to entercomputer system enclosure 401 through one or more pair of intakeapertures (not shown in FIG. 4) in front vented cover 412 in thedirections shown by the intake arrows designated with reference numeral432. In other words, in the embodiment shown in FIG. 4 front ventedcover 412 is an intake cover. Air then flows over or through electronicsdrawers 420, where heat is transferred to the air from heat generatingcomponents within electronics drawers 420, thereby increasing thetemperature of the air as it passes over or through electronics drawers420. Heated air then exits computer system enclosure 401 through one ormore pair of exhaust apertures (not shown in FIG. 4) in rear ventedcover 414 in the directions shown by the exhaust arrows designated byreference numeral 434, where it returns to and mixes with room ambientair. In other words, in the embodiment shown in FIG. 4 rear vented cover414 is an exhaust cover.

FIG. 6 is a perspective view of computer system enclosure 401incorporating the front vented cover 412. Air is drawn into computersystem enclosure 401 through one or more pair of intake apertures infront vented cover 412. These intake apertures are preferably generallytriangular intake apertures, such as the right-side intake apertures 602shown in FIG. 6. Each right-side intake aperture 602 shown in FIG. 6defines the intake of one member of a pair of cross-flow ventilationducts. The left-side intake aperture that defines the intake of theother member of each pair of cross-flow ventilation ducts cannot be seenfrom the right-side perspective shown in FIG. 6, but is a generallytriangular intake aperture on the left side of front vented cover 412that is substantially identical to and in a complimentary orientationwith respect to its mate (i.e., right-side intake aperture 602). Inaddition, front vented cover 412 is preferably shaped to includeright-side and right-side chamfered surfaces where right-side intakeaperture 602 and the left-side intake aperture respectively reside at anangle (e.g., 90° or greater) with respect to one another. This allowsthe cover to hinge open without being impeded by a similar adjacentcover.

The configuration and the relative orientation of each pair of intakeapertures of front vented cover 412 (i.e., intake cover) can be seen inFIGS. 7 a, 9 a and 10, which show analogous (preferably identical)exhaust apertures of rear vented cover 414 (i.e., exhaust cover).Although the front vented cover 412 shown in FIG. 6 includes eight pairof cross-flow ventilation ducts (as indicated by the eight right-sideintake apertures 602 shown therein), any number of pair of cross-flowventilation ducts may be used therein according to the preferredembodiments of the present invention. Likewise, although the rear ventedcover 414 shown in FIG. 9 a includes eight pair of cross-flowventilation ducts (as indicated by the eight pair of exhaust aperturesshown therein), any number of pair of cross-flow ventilation ducts maybe used therein according to the preferred embodiments of the presentinvention.

Preferably, rear vented cover 414 is identical to front vented cover 412to reduce the number of unique parts used in computer system 400, andhence reduce the cost of producing and maintaining computer system 400.In that case, rear vented cover 414 would include cross-flowventilations ducts identical to those of front vented cover 412, andinclude generally triangular exhaust apertures identical to thegenerally triangular intake apertures in front vented cover 412.

FIGS. 7 a-7 d are respectively a partial front view; a section, topview; a partial rear view; and a partial side view of rear vented cover414 (exhaust cover). FIGS. 7 e-7 g are respectively partial sectionalviews of rear vented cover 414 along sections A-A, B-B, and C-C in FIG.7 c. FIG. 7 b shows rear cover 414 attached to rear panel 404 ofcomputer system 401, while FIGS. 7 a and 7 c-7 g show rear cover 414isolated from computer system enclosure 401 for the sake of clarity.FIGS. 7 a-7 g illustrate a single pair of cross-flow ventilation ducts702/704. As noted above, rear vented cover 414 is preferably identicalto front vented cover 412, and hence the description of the rear ventedcover 414 (exhaust cover) below also applies to front vented cover 412(intake cover) although the direction of airflow would be reversed.

FIGS. 8 a-8 b, 9 a-9 b, and 10-12 provide additional views of rearvented cover 414 (exhaust cover). FIGS. 8 a-8 b are respectively a rearview and a section, top view of rear vented cover 414. FIGS. 9 a-9 b arerespectively a front view and a top view of rear vented cover 414. FIG.10 is a partial, front perspective view of rear vented cover 414. FIG.11 is a partial, rear perspective view of the rear vented cover 414.FIG. 12 is an enlarged partial, rear perspective view of a single pairof cross-flow ventilation ducts of rear vented cover 414.

Referring now to FIGS. 7 a-7 d, a lower duct 702 is formed in rearvented cover 414 (exhaust cover) between a generally triangular exhaustaperture 712 and an intake port 722. The intake port 722 occupiessubstantially one-half (right side from the perspective shown in FIG. 7c) surface area of rear cover 414 where rear vented cover 414 abutsagainst rear panel 404 of computer system enclosure 401. Intake port 722is substantially rectangular except for a relatively small, generallytriangularly shaped surface 723 (shown in FIG. 7 c) at one cornerthereof. An upper duct 704 is formed in rear vented cover 414 between agenerally triangular exhaust aperture 714 and an intake port 724. Theintake port 724, which is coplanar with intake port 722, occupiessubstantially one-half (left side from the perspective shown in FIG. 7c) surface area of rear cover 414 where rear vented cover 414 abutsagainst rear panel 404 of computer system enclosure 401. Intake port 724is substantially rectangular except for a relatively small, generallytriangularly shaped surface 725 (shown in FIG. 7 c) at one cornerthereof. It is important to note that only relatively small, triangularsurfaces 723 and 725 block the flow of air near where rear vented cover414 abuts against rear panel 404 of computer system enclosure 401.Accordingly, airflow is improved relative to conventional vented coversdue to reduced surfaces blocking airflow close to the airflow aperture405 in rear panel 404 through which air exits computer system enclosure401.

Lower duct 702 and upper duct 704 are “cross-flow” in that they crossand bypass one another. Accordingly, the direction of airflow in lowerduct 702 (shown in FIGS. 7 a-7 g by arrows designated with referencenumeral 732) crosses the direction of airflow in upper duct 704 (shownin FIGS. 7 a-7 g by arrows designated with reference numeral 734). Bothlower duct 702 and upper duct 704 include an acoustic noise reductionlining, such as an acoustic foam lining. Examples of acoustic noisereduction lining include open and closed cell, flexible polyurethane,polyimide, melamine and other foams available from Soundcoat Company ofDeer Park, N.Y. (These examples are representative of a class ofproducts serving similar functions and do not imply any particularrequirement for the specific characteristics of these products.)Preferably, both lower duct 702 and upper duct 704 are lined with anacoustic noise reduction lining in their entirety, i.e., from theirintake ports 722, 724 to their exhaust apertures 712, 714.Alternatively, selected portions of lower duct 702 and upper duct 704may be lined with an acoustic noise reduction lining.

The acoustic noise reduction lining may be, for example, flat,self-adhesive panels that are cut to conform to the surface of thecross-flow ventilation ducts 702, 704 and applied (in tile-like fashion)thereto. Alternatively, the acoustic noise reduction lining may beprovided by any other technique known in the art (e.g., cutting,molding, spraying, etc.).

As mentioned above, FIGS. 7 e-7 g respectively show three parallelpartial sectional views of rear vented cover 414 along sections A-A,B-B, and C-C in FIG. 7 c. As shown in FIG. 7 e, at cross-section A-Alower duct 702 and upper duct 704 are preferably each generallytriangular. As shown in FIG. 7 f, at cross-section B-B lower duct 702and upper duct 704 are preferably each generally rectangular. Thegenerally rectangular shape of lower duct 702 and upper duct 704 atcross-section B-B is also shown (as hidden lines) in FIG. 12. As shownin FIG. 7 g, at cross-section C-C lower duct 702 and upper duct 704 arepreferably each generally triangular.

To reduce airflow resistance, it is preferable to maintain the samecross-sectional area throughout the cross-flow ventilation ducts 702,704. The area of lower duct 702 remains substantially constant betweencross-sections A-A and B-B and between cross-sections B-B and C-C, asdoes the area of upper duct 704. Additionally, the cross-sectional areaof lower duct 702 preferably remains substantially constant (orincreases) from cross-section A-A to exhaust aperture 712, while thecross-sectional shape remains generally the same. Likewise, thecross-sectional area of upper duct 704 preferably remains substantiallyconstant (or increases) from cross-section C-C to exhaust aperture 714,while the cross-sectional shape remains generally the same. Similarly,the cross-sectional area of intake port 722 is preferably at least aslarge as the cross-sectional area of lower duct 702 at cross-sectionC-C, and the cross-sectional area of intake port 724 is preferably atleast as large as the cross-sectional area of upper duct 704 atcross-section A-A. Accordingly, airflow is improved relative toconventional vented covers because air flows substantially unrestrictedalong the entire path of the cross-flow ventilation ducts 702, 704.

As mentioned above, exhaust apertures 712, 714 are preferably generallytriangular. This is preferable to maintain the cross-sectional shape oflower duct 702 from cross-section A-A to exhaust aperture 712, andmaintain the cross-sectional shape of upper duct 704 from cross-sectionC-C to exhaust aperture 714.

In general, it is desirable to avoid tight bends in the cross-flowventilation ducts to reduce airflow resistance and increase air movingefficiency (otherwise, a larger and/or additional air moving devices maybe necessitated). Consequently, the cross-flow ventilation ducts 702,704 preferably present gently curved surfaces.

Airflow resistance is reduced by reducing surfaces perpendicular andclose to where air initially exits through the airflow aperture 405 inrear panel 404. In this regard, only relatively small, triangularsurfaces 723 and 725 block airflow where the air initial initially exitsthrough the airflow aperture 405 in rear panel 404, i.e., intake ports722, 724 occupy substantially the entire area of the airflow aperture405 in the rear panel 404 where rear vented cover 414 abuts against rearpanel 404. Accordingly, airflow is improved relative to conventionalvented covers due to reduced surfaces blocking airflow close to theairflow aperture 405 in rear panel 404 through which air exits computersystem enclosure 401. For example, in the conventional exhaust covers220, 320 shown in FIGS. 2 and 3, central acoustic foam block 224 andcentral acoustic foam panel 324 disadvantageously present largeroadblocks to exiting air.

It is also generally desirable for air/noise to stay in the cross-flowventilation ducts 702, 704 for as long as possible to increaseattenuation efficiency. Consequently, the cross-flow ventilation ducts702, 704 each preferably provide a relatively long air path. This longair path allows the surface area of the sound absorbing material (i.e.,the acoustic noise reduction lining) to be increased relative toconventional vented covers, thereby improving acoustic attenuation. Thelong air path also reduces the “line of sight” to noise sources, whichfurther improves acoustic attenuation. In this case, “line of sight”means that if you can easily see through the ducts to the other side ofthe cover, then noise has a similar, easy way out of the cover. Reducing“line of sight” reduces the level of noise that can pass through.

Preferably, in large sizes, rear vented cover 414 includes a metal outershell into which is/are inserted one or more plastic inserts thatprovide cross-flow ventilation ducts 702, 704. The outer metal shellcould provide electromagnetic interference protection. For smallerapplications such as PC tower sizes, the outer shell could be plastic orother nonmetal material. The plastic inserts are preferably made fromthermally formed plastic. For example, a flat sheet of plastic may beheated to form the bends (shown in FIG. 12) that define the gentlycurved surface of cross-flow ventilation ducts 702, 704. Alternatively,one or more metal inserts may be used in lieu of plastic inserts. Forexample, metal inserts may be formed by working sheet metal using anytechnique known in the art (e.g., bending, welding, riveting, adhering,etc.). Advantageously, plastic inserts reduce the weight of rear ventedcover 414 relative to using metal inserts. Also, it may be desirable toform the insert from an acoustic noise reduction material.

It is important to note that the vented cover according to the preferredembodiments of the present invention has a relatively thin depth becausethe cross-flow ventilation ducts 702, 704 cross and bypass each other ina very space efficient manner. This contrasts with conventional ventedcovers, which typically are relatively thick and thereby significantlyand disadvantageously increase the footprint of the computer systemenclosure to which they are attached.

One skilled in the art will appreciate that many variations are possiblewithin the scope of the present invention. Although the preferredembodiments of the present invention is described herein within thecontext of an enclosure for containing a computer system, those skilledin the art will appreciate that the present invention may be practicedwith an enclosure for containing any type of system. For example, thepresent invention may be practiced with an enclosure for an airtreatment system, such as an air filter, air cleaner, dehumidifier, airconditioner, heater, or the like in lieu of an enclosure containing acomputer system. Thus, while the present invention has been particularlyshown and described with reference to preferred embodiments thereof, itwill be understood by those skilled in the art that these and otherchanges in form and details may be made therein without departing fromthe spirit and scope of the present invention.

1. A method for acoustic noise reduction in a system, comprising:providing an enclosure for containing components of the system, theenclosure including a front panel, a rear panel, a top panel, a bottompanel, and two side panels; providing a vented cover positioned relativeto the enclosure so that the vented cover abuts against a selected oneof the panels having an airflow aperture, the vented cover including apair of cross-flow ventilation ducts, wherein one of the cross-flowventilation ducts crosses the other of the cross-flow ventilation ductsso that in an intermediate cross-section of the vented cover air movesin one of the cross-flow ventilation ducts in a direction substantiallyopposite to that in the other of the cross-flow ventilation ducts, andwherein at least a portion of each of the cross-flow ventilation ductsincludes an acoustic noise reduction lining; causing external air toenter the enclosure and then exit the enclosure, wherein the externalair enters the enclosure or exits the enclosure through the cross-flowventilation ducts of the vented cover.
 2. A method for acoustic noisereduction in a computer system, comprising: providing an enclosure forcontaining an electronic component package of the computer system, theenclosure including a front panel, a rear panel, a top panel, a bottompanel, and two side panels; providing a vented cover positioned relativeto the enclosure so that the vented cover abuts against a selected oneof the panels having an airflow aperture, the vented cover including apair of cross-flow ventilation ducts, wherein one of the cross-flowventilation ducts crosses the other of the cross-flow ventilation ductsso that in an intermediate cross-section of the vented cover air movesin one of the cross-flow ventilation ducts in a direction substantiallyopposite to that in the other of the cross-flow ventilation ducts, andwherein at least a portion of each of the cross-flow ventilation ductsincludes an acoustic noise reduction lining; causing external air toenter the enclosure and then exit the enclosure, wherein the externalair enters the enclosure or exits the enclosure through the cross-flowventilation ducts of the vented cover.
 3. A method for acoustic noisereduction in a system, comprising: providing an enclosure for containingcomponents of the system, the enclosure including a front panel, a rearpanel, a top panel, a bottom panel, and two side panels, wherein thesystem includes an air moving device for passing air through theenclosure; providing a vented cover positioned relative to the enclosureso that the vented cover abuts against a selected one of the panelshaving an airflow aperture, the vented cover including a first pair ofcross-flow ventilation ducts, wherein at least a portion of each of thecross-flow ventilation ducts includes an acoustic noise reductionlining, wherein the air moving device passes air through the enclosureinto or from the cross-flow ventilation ducts, and wherein thecross-flow ventilation ducts are configured so that in an intermediatecross-section of the vented cover air moves in one of the cross-flowventilations ducts in a direction substantially opposite to that in theother of the cross-flow ventilation ducts.
 4. The method as recited inclaim 3, wherein the vented cover includes a second pair of cross-flowventilation ducts generally identical to the first pair, and wherein thesecond pair of cross-flow ventilation ducts is disposed in a stackedrelationship above the first pair.
 5. The method as recited in claim 4,wherein the vented cover includes a third pair of cross-flow ventilationducts generally identical to the first pair, and wherein the third pairof cross-flow ventilation ducts is disposed in a stacked relationshipabove the second pair.
 6. The method as recited in claim 3, wherein thecross-flow ventilation ducts are generally rectangular in theintermediate cross-section of the vented cover.
 7. The method as recitedin claim 6, wherein the cross-flow ventilation ducts are generallytriangular in one or more cross-sections of the vented cover outside theintermediate cross-section.